1. Field of the Invention
The present invention relates generally to a wireless telephone equipment, and more particularly to an improved wireless telephone equipment which operates as a cordless telephone within call range of a base unit of a cordless telephone system and operates as a cellular telephone out of the call range of the cordless telephone.
2. Description of the Related Art
A cellular telephone equipment has been recently used because a user can place and receive telephone calls at any time and at any place. Also, a cordless telephone equipment in which radio transmission is performed in place of wire communication.
In the prior art, a cordless telephone system is provided with a cordless base station and at least one portable unit of cordless telephone equipment. The cordless base station is connected to a wire telephone line, and the radio transmission is performed between the cordless base station and the portable unit of cordless telephone equipment. For example, in cases where the cordless base station is set in the home, the portable unit is used in a surrounding area of the home to allow the user to place and receive telephone calls. The surrounding area is usually a circular area up to several hundreds of meters in radius for clear reliable communication. In this case, the cost of a cordless telephone call is the same as the cost of a wire telephone call because the telephone communication is performed through a subscriber's telephone line.
In contrast, a cellular telephone area is divided into a large number of cells in a cellular telephone system in which cellular telephone communication is performed by utilizing the cellular telephone equipment. In this case, a cellular telephone base station is arranged at each of the cells. For example, in cases where a user positioned in a surrounding area of one of the cellular telephone base stations places a telephone call by using the cellular telephone equipment, the telephone call is transmitted to the cellular phone base station. The surrounding area is usually a circular area ranging from several kirometers to tens of kirometers in radius for clear reliable communication. Therefore, the cellular telephone equipment can be used in any cell to allow the user to place and receive telephone calls. However, the cost of a cellular telephone call is considerably higher than the cost of the wire telephone call because a large number of cellular telephone base stations must be arranged at the cells of which the intervals range from several kirometers to tens of kirometers.
Therefore, a cellular and cordless telephone equipment which can operate as both a cellular telephone equipment and a portable unit of cordless telephone equipment has been proposed. The cellular and cordless telephone equipment automatically or manually operates as the cordless telephone equipment within call range of a cordless base station of a cellular and cordless telephone system. The cellular and cordless telephone equipment was laid open to public inspection under Provisional Publication No. 1621/91 (H31621).
2.1. Previously Proposed Art
The conventional cellular and cordless telephone equipment laid open to public inspection under Provisional Publication No. 1621/91 is described with reference to FIGS. 1, to 3.
FIG. 1 is a block diagram of the conventional cellular and cordless telephone equipment. FIG. 2 is a block diagram of both a cordless telephone transceiver and a cellular telephone transceiver included in the conventional cellular and cordless telephone equipment shown in FIG. 1.
As shown in FIG. 1, the conventional cellular and cordless telephone equipment 11 includes a microphone 12, a speaker 13, an audio switch 14 for switching from a cellular side (a cordless side) to the cordless side (the cellular side), a microcomputer 15 for controlling the conventional cellular and cordless telephone equipment 11, a cordless telephone transceiver 16 arranged at the cordless side, a cellular telephone transceiver 17 arranged at the cellular side, a key-pad 18, and a display 19.
The cordless telephone transceiver 16 includes a cordless side antenna 20, a cordless receiver 21 for receiving a modulated signal of an incoming call through the antenna 20, a cordless transmitter 22 for transmitting a modulated signal of an outgoing call through the antenna 20, and an audio circuitry 23 for amplifying an audio signal to give voice from the speaker 13 or amplifying an audio signal received in the microphone 12 to modulate the audio signal in the cordless transmitter 22.
The cellular telephone transceiver 17 includes a cellular side antenna 24, a cellular receiver 25 for receiving a modulated signal of an incoming call through the antenna 24, a cellular transmitter 26 for transmitting a modulated signal of an outgoing call through the antenna 24, and an audio circuitry 27 for amplifying an audio signal to give voice from the speaker 13 or amplifying an audio signal received in the microphone 12 to modulate the audio signal in the cellular transmitter 26.
As shown in FIG. 2, the cordless receiver 21 includes a band-pass filter 28 for filtering the modulated signal of the incoming call transmitted from the antenna 20, and a demodulator 29 for demodulating the modulated signal filtered to produce the audio signal. The audio signal produced in the demodulator 29 is amplified in the audio circuitry 23. The cordless transmitter 22 includes a modulator 30 for modulating a carrier with the audio signal amplified in the audio circuitry 23 to produce the modulated signal of the outgoing call, and a band-pass filter 31 for filtering the modulated signal produced in the modulator 30. The modulated signal received in the antenna 20 is transferred to the cordless receiver 21 through a coupling circuitry 32, and the modulated signal filtered in the band-pass-pass filter 31 is transferred to the antenna 20 through the coupling circuitry 32.
Also, the cellular receiver 25 includes a band-pass filter 33 for filtering the modulated signal of the incoming call transmitted from the antenna 24, and a demodulator 34 for demodulating the modulated signal filtered to produce the audio signal. The audio signal produced in the demodulator 34 is amplified in the audio circuitry 27. The cellular transmitter 26 includes a modulator 35 for modulating a carrier with the audio signal amplified in the audio circuitry 27 to produce the modulated signal of the outgoing call, and a band-pass filter 36 for filtering the modulated signal produced in the modulator 35. The modulated signal received in the antenna 24 is transferred to the cellular receiver 25 through a coupling circuitry 37, and the modulated signal filtered in the band-pass filter 36 is transferred to the antenna 24 through the coupling circuitry 37.
In the above configuration, in cases where the conventional cellular and cordless telephone equipment 11 is positioned within call range of a cordless base station of the cellular and cordless telephone system, the equipment 11 automatically operates as a portable unit of the cordless telephone equipment under control of the microcomputer 15. That is, the cordless telephone transceiver 16 is set in an operating condition, while the cellular telephone transceiver 17 is set in a non-operating condition. Also, the audio switch 14 is switched to the cordless side. That is, a terminal A connected to the speaker 13 is connected with a terminal A2 connected to the audio circuitry 23, and a terminal B connected to the microphone 12 is connected with a terminal B2 connected to the audio circuitry 23.
Therefore, voice of the user is transferred to the audio circuitry 23 as an audio signal through the microphone 12 and the audio switch 14. After the audio signal is amplified in the audio circuitry 23, a carrier is modulated with the audio signal amplified to a modulated signal in the modulator 30, and the modulated signal is filtered in the band-pass filter 31. As shown in FIG. 3, a frequency of the modulated signal filtered in the band-pass filter 31 ranges from 49.67 MHz to 49.99 MHz. Therefore, the modulated signal of which the frequency ranges from 49.67 MHz to 49.99 MHz is transmitted from the antenna 20 to the cordless base station of the cellular and cordless telephone system.
Also, a modulated signal transmitted from the cordless base station is received in the antenna 20. Thereafter, the modulated signal is filtered in the band-pass filter 28 as shown in FIG. 3. That is, a frequency of the modulated signal filtered in the band-pass filter 28 ranges from 46.61 MHz to 46.93 MHz. Thereafter, the modulated signal filtered is demodulated in the demodulator 29 to produce an audio signal. The audio signal is transferred to the speaker 13 through the audio circuitry 23 and the audio switch 14. Therefore, the user can hear voice of a sender.
In contrast, in cases where the conventional cellular and cordless telephone equipment 11 moves out of the call range of a cordless base station of the cellular and cordless telephone system, the equipment 11 automatically operates as a cellular telephone equipment under control of the microcomputer 15. That is, the cordless telephone transceiver 16 is set in a non-operating condition, while the cellular telephone transceiver 17 is set in an operating condition. Also, the audio switch 14 is switched to the cellular side. That is, the terminal A is connected with a terminal A1 connected to the audio circuitry 27, and the terminal B is connected with a terminal B1 connected to the audio circuitry 27.
Therefore, voice of the user is transferred to the audio circuitry 27 as an audio signal through the microphone 12 and the audio switch 14. After the audio signal is amplified in the audio circuitry 27, a carrier is modulated with the audio signal amplified to a modulated signal in the modulator 35, and the modulated signal is filtered in the band-pass filter 36. As shown in FIG. 3, a frequency of the modulated signal filtered in the band-pass filter 36 ranges from 824 MHz to 849 MHz. Therefore, the modulated signal of which the frequency ranges from 824 MHz to 849 MHz is transmitted from the antenna 24 to a cellular telephone base station of the cellular and cordless telephone system.
Also, a modulated signal transmitted from the cellular telephone base station is received in the antenna 24. Thereafter, the modulated signal is filtered in the band-pass filter 33 as shown in FIG. 3. That is, a frequency of the modulated signal filtered in the band-pass filter 33 ranges from 869 MHz to 894 MHz. Thereafter, the modulated signal filtered is demodulated in the demodulator 34 to produce an audio signal. The audio signal is transferred to the speaker 13 through the audio circuitry 27 and the audio switch 14. Therefore, the user can hear voice of a sender.
It is preferred that an antenna 38 be utilized in place of the antennas 20, 24. In this case, a low-pass filter 39 is provided for the cordless telephone transceiver 16, and a high-pass filter 40 is provided for the cellular telephone transceiver 17.
Accordingly, the conventional cellular and cordless telephone equipment 11 can automatically operate as the portable unit of the cordless telephone equipment under control of the microcomputer 15 in cases where the equipment 11 is positioned within the call range of the cordless base station of the cellular and cordless telephone system.
Also, the conventional cellular and cordless telephone equipment 11 can automatically operate as the cellular telephone equipment under control of the microcomputer 15 even though the equipment 11 moves out of the call range of the cordless base station of the cellular and cordless telephone system.
2--2 Problems to be Solved by the Invention
However, the cordless side antenna 20, the cordless receiver 21, the cordless transmitter 22, and the audio circuitry 23 are required for the conventional cellular and cordless telephone equipment 11 to operate as the portable unit of the cordless telephone equipment. Also, the cellular side antenna 24, the cellular receiver 25, the cellular transmitter 26, and the audio circuitry 27 are required for the conventional cellular and cordless telephone equipment 11 to operate as the cellular telephone equipment. In addition, the cordless transceiver 16 is provided with the base-band filters 28, 31, and the cellular transceiver 25 is provided with the base-band filters 33, 36. As a result, the size of the equipment 11 becomes large, while a small-sized cellular and cordless telephone equipment is required from a standpoint of the portability. Also, the weight of the equipment 11 becomes heavy, while a lightweight cellular and cordless telephone equipment is required from a standpoint of the portability. In addition, the equipment 11 becomes expensive, while a cheap cellular and cordless telephone equipment is required from a standpoint of the prevalence.